This is definitely part of the Kava journey. I've thrown up three times doing kava over a 3 year period and I think I now understand the balances involved. There is something in Kava that is repellant that does indeed make one want to not eat it and directly suggests to the body that it should throw up. I think I read that it is a chemical that makes animals not want to eat it, so it has an evolutionary purpose? So anything that makes it 'more gross' is even harder to deal with. One of my bad events was with micronized. I think the latest batches of GHK micronized are even smaller than before? Basically, having that gritty quality doesn't help matters. I personally get much closer to that state on micronized than with other forms. That said, I did just buy 2 new bags of micronized from them as I want to explore the new size. This issue is very personal. Everyone responds a bit differently to the different forms and tastes.
Re-reading your post, I just realized something. I personally find naseau and throwing up to be two different things, though extreme naseau can cause throwing up. For naseau, as is mentioned above, ginger is the trick. Even with Wow, it is a totally different experience for me with ginger. However - be careful - things with the word 'ginger' on them aren't necessarily ginger, such as most ginger ale's at Safeway. I like "Bruce Cost" brand and Reeds "Extra Ginger" version. 26 grams of ginger in there per bottle! That is the highest verified content I know of. This will indeed make a difference on the naseau. A big difference.
However, people are talking about putting it in with the kava? I can't do that. For me it foams a ton when I combine them, and I'm back to the throwing up thing
. So I use it as a chaser. I started with Pellegrino style blood orange or aranicita, those both deal with the taste much quicker and better than Reed's, but don't help with the nasuea. I had tried Kava in those too, but the foaming was no good for me back then as well. Similarly, I know some people blend micronized for a minute and then drink it, that adds a lot of air to the mixture, and again, as that goes down I'm back at wanting to throw up. Guess I'm a bit delicate. The easiest one of those two to find is the Reeds Extra Ginger, give that a try as a chaser. There are a bunch of other premium ginger brands like Bruce Cost as well that use real actual ginger in high qualities. My wife makes her own with lime and real ginger and soda water. If you can put your kava in it and deal with the foam, all the better as you don't want soooo much liquid.
The other thing I learned on this forum about nasuea is when doing something like Wow, I do a full cup and then do it again 30 or 40 minutes later. A full cup can be a lot. There is some known chemical that grows in concentration in the blood too quickly if you take that much at once. So the recommendation is to do half, wait no less than 8 min and don't wait too much longer, and finish the cup. The kavain and other good things will still properly grow to high levels but the one that causes nasuea will be moderated quite a bit. I don't acutally know how well this works, but 'seems' to help. It is just something someone else claimed was good to do.
And realize that with blends like Wow or Stone, well, naseau even if moderated is part of this game. Even a few tbs of instant will cause some naseau.
Do we know if the naseau is from anything other than the 5 main kavalactones? I know one of them is very involved, was it DHK? But maybe there is another chemical as well? And I don't think the one that makes one want to regurgitate it is from one of the 5 kavalactones?
Yeah, the original 
